Storage of biological and chemical samples is becoming widespread in biotechnological and medical industries. Many of these samples must be stored at or below freezing temperatures. Generally speaking, a regular freezer operates from −5° C. to −20° C., an ultra-low temperature freezer operates from about −50° C. to about −90° C. (preferably at about −80° C.) and a cryogenic freezer operates from about −140° C. to −196° C. (the boiling point of liquid nitrogen).
The assignee of the present application has filed co-pending application Ser. No. 12/020,246 entitled “Automated Storage And Retrieval System For Storing Biological Or Chemical Samples At Ultra-Low Temperatures”, by Robert P. Cloutier, Julian Warhurst, Behrouz Zandi, James O'Toole and Halvard Solbert, on Jan. 25, 2008, which is hereby incorporated by reference. This co-pending application describes an automated, ultra-low temperature sample storage and retrieval system having storage racks mounted within an insulated, ultra-low temperature freezer compartment (−80° C.). A mechanical robot is provided within the ultra-low temperature storage compartment to place sample storage containers in the storage racks and retrieve the storage containers from the racks. The sample storage containers are typically SBS footprint compatible, and normally take the form of microtiter plates, tube storage racks, reservoirs or other SBS format containers. The robot communicates with an access module in order to introduce sample storage containers into the system and retrieve the containers for use outside of the system. The freezer racks have a capacity of several hundred or more sample storage containers, such as microtiter plates or tube storage racks. The present invention is directed to a tube picking apparatus that is particularly well suited for use in the automated ultra-low temperature storage and retrieval system disclosed in the above incorporated patent application, but also may be useful in other systems as well.
As explained in the above incorporated patent application, biological samples stored in ultra-low temperature systems are often contained in sealed plastic laboratory tubes or vials having a diameter of 8 mm or larger. Larger tubes are sometimes called vials in the art, but both are referred herein as tubes or storage tubes. In any event, the tubes or vials are typically held in tube storage containers (sometimes referred to as tube racks) in arrays of, for example, 96, 48 or 24 tubes. The tube racks, as mentioned, typically have SBS footprint compatible dimensions. In some cases, a two-dimensional bar code containing identifying information is adhered to the bottom of the storage tubes and is able to be read through openings in the bottom of the SBS tube racks. The above incorporated patent application discloses the use of a two-dimensional bar code reader at the access module for this purpose. The system control system is able to keep track of the location of samples within the system based on that information. In many cases, however, two-dimensional bar codes are not adhered to the bottom of the storage tubes. In many situations, a one-dimensional bar code containing identifying information is placed manually on the sidewall of the storage tube. The variety of positions and orientations of manually placed one-dimensional bar code labels makes them difficult to read in an automated system, especially within the ultra-low temperature environment or in the access module.
As explained in the above incorporated patent application, it is not normally desirable to remove an entire SBS storage rack from the system when only one or a few storage tubes from a given rack are desired to be retrieved. The removal procedure allows for the ingress of moisture into the ultra-low temperature storage compartment, and also renders the other samples held in the same SBS tube rack susceptible to thawing, at least partially, even if the tube rack is removed from the system temporarily. The above incorporated patent application also explains that while tube picking mechanisms are generally known in the art, the environment within the ultra-low temperature freezer compartment is typically too cold to ensure reliable operation of conventional tube picking mechanisms.
In order to address these issues, the incorporated, co-pending patent application provides a tube picking chamber adjacent the freezer compartment, preferably incorporated into the insulated freezer door. A retractable shuttle door is located between the tube picking chamber and the ultra-low temperature storage compartment. A reach arm for the robot within the ultra-low temperature freezer compartment supplies a selected SBS tube rack (i.e., a source rack) to a specific location in freezer compartment that can also be accessed by a robotic shuttle constituting part of the tube picking mechanism. Picked tubes are loaded into another tube rack (i.e., a destination rack) that is intended to exit the system. The shuttle door for the tube picking chamber normally remains closed, isolating the tube picking chamber from the ultra-low temperature freezer compartment under normal storage conditions. When use of the tube picking mechanism is requested, dry gas is introduced into the tube picking chamber with the shuttle door closed in order to reduce the relative humidity within the chamber. A relative humidity sensor is located within the tube picking chamber for this purpose. When the relative humidity has been lowered to the desirable level, for example less than 2% relative humidity, the shuttle door is opened and cold air from the ultra-low temperature freezer compartment is allowed to flow into the tube picking chamber. A temperature sensor is also located in the tube picking chamber. The shuttle door is opened and closed as necessary to maintain the temperature in the tube picking chamber at a freezing temperature that is above the ultra-low temperature (−80° C.) in the storage compartment, preferably −5° C. to −25° C., e.g. about −20° C. In this manner, the tube picking mechanism, and its mechanical and electrical components, can operate in a less harsh environment which greatly improves reliability. On the other hand, by maintaining the tube picking chamber at a subfreezing temperature, the other samples in the pertinent source racks need not exit the system in order to retrieve the desired storage tube or tubes. This not only protects the other samples from premature thaw and harm, but also reduces the risk of moisture flow into the ultra-low temperature freezer compartment. Further, because the relative humidity is maintained at a low level within the tube picking compartment, tube racks can be shuttled in and out of the tube picking compartment at a relatively fast pace compared to shuttling through the main access module. Fast pace shuttling shortens exposure time outside of the −80° environment for samples not selected for retrieval.
The prior art includes tube picking mechanisms used in −20° C. freezer systems. With tube picking mechanisms for −20° C. freezer systems, it is known to use a cache for temporarily holding picked storage tubes as the tubes are being transferred between source racks and a destination rack. However, these tube picking mechanisms are typically located within the main freezer compartment, and are typically too bulky for use in the smaller-sized tube picking chamber disclosed in the above incorporated patent application. In the −80° C. system described in the incorporated co-pending patent application, it is important to keep the tube picking chamber relatively small because its existence and use is generally a burden to the cooling system.
While the system disclosed in the above-discussed incorporated patent application is designed to be used with a wide array of tube picking mechanisms, an object of the present invention is to provide a system that can efficiently and reliably shuttle tube storage racks from the ultra-low temperature storage compartment (−80° C.) into the tube picking chamber (−20° C.) at the given temperatures, as well as effectively and reliably transfer picked tubes from the retrieved source racks into a suitable destination rack designated to be exported from the system with the selected samples.
Another object of the invention, as mentioned previously, is to design a practical manner for reading one-dimensional bar codes located on the sidewall of the storage tubes.
Yet, another object of the present invention is to improve the efficiency and consistency of cooling within the tube picking chamber.